The present invention relates to the field of containers for maintaining liquids and solid materials such as food at a substantially constant temperature over a relatively long period of time. One highly successful device for accomplishing this objective is a Dewar flask or thermos bottle. Such a container employs a double wall filler which may be made of metal, or glass and from which air is substantially evacuated.
It is known in the prior art to provide relatively narrow mouth thermos bottles which are well adapted for storing and pouring liquids and which utilize a tall and relatively small diameter vacuum filler.
Wide mouth thermos bottles employ a vacuum filler of a larger diameter and have a protective liner which closely conforms to the internal wall of the wide mouth filler. A wide mouth thermos, while being well suited to the storing and dispensing of solid and semi-solid foods such as soups has the disadvantage of a lower thermal insulating capability than the narrow mouth design. Further, liquids are more difficult to pour without spilling.
It is accordingly an object of the present invention to obtain the benefits of a wide mouth thermos design and the advantages of a narrow mouth thermos.
It is another object of the present invention to provide a thermos which uses a wide opening vacuum filler but has the pouring characteristics of a narrow mouth thermos.
It is a further object of the present invention to provide a lined, wide mouth thermos with a stopper having a narrow pouring opening.
It is another object of the present invention to provide a compound stopper which is capable of converting a wide mouth thermos bottle into a narrow mouth thermos bottle so that the benefits of each design can be obtained.
It is yet another object of the present invention to provide a thermos bottle which can be used as either a wide mouth thermos bottle or a narrow mouth thermos bottle as desired.
Other objects of the present invention will become apparent from the remaining portion of the specification.